The present invention relates to a laser device, and more particularly to connection structure of discharge electrodes in a laser device and a laser device including the discharge electrodes.
A laser device which discharges electricity between discharge electrodes to excite a laser medium, thereby oscillating a laser beam has been hitherto known and is shown, for example, in Japanese Patent Laid-open No. 1-268078 Official Gazette. FIG. 10 shows the structure of an excimer laser device disclosed in the aforesaid Official Gazette, and FIG. 11 shows the structure of discharge electrodes in the excimer laser device disclosed in the aforesaid Official Gazette.
In FIG. 10 and FIG. 11, an excimer laser device 101 includes a laser chamber 102 sealing in a laser medium such as laser gases. Inside the laser chamber 102, a pair of discharge electrodes 105A and 105B composed of an anode 105A and a cathode 105B are disposed facing each other. The anode 105A is fixed to a conductive anode base 106, and the cathode 105B is fixed to an insulating cathode base 108.
A pair of preionization electrodes 118 and 118 are disposed facing each other on both sides of the discharge electrodes 105A and 105B, and a high-voltage current is supplied from a high voltage power supply though a preionization circuit and a current introducing terminal which are not illustrated, thereby performing preionization.
Inside the laser chamber 102, a cross flow fan 114 for sending laser gases into a space between the discharge electrodes 105A and 105B and a heat exchanger 103 for cooling the laser gases heated by electric discharge are disposed at predetermined positions. Electricity is discharged between the anode 105A and the cathode 105B to excite laser gases, shown by the arrows G, flowing through the space between the anode 105A and the cathode 105B, thereby oscillating a laser beam.
The anode base 106 and the cathode base 108 are supported by support posts 110 with a predetermined space between them. The anode base 106 and the laser chamber 102 are electrically connected with a plurality of return plates 109 arranged at predetermined intervals in the longitudinal direction of the discharge electrodes 105A and 105B. It should be mentioned that connection points of the return plates 109 and the laser chamber 102 are not clearly illustrated in the aforesaid Official Gazette. Each of the return plates 109 is made of a conductive plate-shaped member, and disposed parallel to the gas flow G so that a portion 109A with a thin plate thickness faces to the upper reaches and the lower reaches of the gas flow G with respect to the gas flow.
The prior art disclosed in the aforesaid Japanese Patent Laid-open No. 1-268078 Official Gazette, however, has the following problems.
Namely, in the prior art, in order to smoothly supply an electric current to the whole area in the longitudinal direction of the anode 105A to suitably discharge electricity, the plurality of return plates 109 are provided in the whole area in the longitudinal direction. When the excimer laser device 101 is assembled, the plurality of return plates 109 need to be attached one by one so as to connect the anode base 106 and the laser chamber 102, which requires a lot of trouble over assembling.
Furthermore, the discharge electrodes 105A and 105B become worn-out as the result of electric discharge, and hence they need to be replaced regularly. Every time the discharge electrodes 105A and 105B are replaced as above, the plurality of return plates 109 need to be attached/detached, which takes a lot of time and labor.
The present invention is made to solve the problems in the aforesaid art, and its object is to provide a discharge electrode for a laser device allowing return plates to be easily attached/detached and a laser device with the discharge electrode.
To attain the aforesaid object, a discharge electrode for a laser device according to the present invention has structure in which a pair of an anode and a cathode, provided facing each other inside a laser chamber sealing in laser gases, for discharging electricity to excite the laser gases flowing through a space between them, thereby oscillating a laser beam, a conductive anode base for holding the anode, an insulating cathode base for holding the cathode, and a plurality of return plates for electrically connecting the anode base and the laser chamber and supplying an electric current to the anode are provided, and in which upper portions and lower portions of the return plates are connected respectively with an upper fixed plate and a lower fixed plate.
Furthermore, a laser device according to the present invention has structure in which a pair of an anode and a cathode, provided facing each other inside a laser chamber sealing in laser gases, for discharging electricity to excite the laser gases flowing through a space between them, thereby oscillating a laser beam, a conductive anode base for holding the anode, an insulating cathode base for holding the cathode, and a plurality of return plates for electrically connecting the anode base and the laser chamber and supplying an electric current to the anode are provided, and in which upper portions and lower portions of the return plates are connected respectively with an upper fixed plate and a lower fixed plate.
According to the aforesaid structure, the plurality of return plates are integrated at the upper and lower portions thereof to be formed into a unit. Thereby, when the return plates are attached/detached, each unit of return plates may be attached/detached, which saves a lot of time and labor compared with a case where a plurality of return plates are attached.
Moreover, the discharge electrode for the laser device and the laser device may each have structure in which the return plates are disposed almost parallel to gas flow of the laser gases flowing through the space between the discharge electrodes.
According to the aforesaid structure, the return plates rectify the gas flow of the laser gases, thereby making the flow of the laser gases smooth and increasing flow velocity. As a result, electric discharge is stabilized, and the power of the laser beam is raised.